Known methods to couple light guide filaments to semiconductor radiators have many difficulties associated therewith due to the small diameter of the cooperating opto-electronic elements. The light guides made in accordance with this method have only mediocre efficiency.
"Applied Optics", Vol. 14, No. 12, Dec. 1975, pp. 2815 to 2816 describes methods to couple optical fibers to semiconductor lasers. The ends of the light guide are melted so that, instead of a flat end portion, a semispherical lens dome ought to result. Couplings for light guide filaments made according to this method do not, however, have the necessary semispherical shape of the core necessary for low-loss coupling. Rather, upon melting, the cladding or jacket material either becomes plastic before the core material so that it pulls in, forming a pupil-like orifice, or the core material becomes soft before the cladding material and, under the influence of surface tension, only a flat lens with long focal length will result at the end of the fiber. The desired, approximately semispherical shape of the end of the fiber with a spherical radius which corresponds approximately to the radius of the core was obtained only in a single case under special experimental conditions which were not transferable to routine manufacture of other light guide fibers.